This invention relates to new nitrogen-containing additives useful as agents for decreasing the cloud point of hydrocarbon middle distillates (fuel oils, gas oils) and to the middle distillates compositions containing said additives.
The oil distillates concerned by the invention consist of middle distillates (fuel oil, gas oil) distilling in the range (ASTM standard D 86-87) of 150.degree. to 450.degree. C. The gas oils more particularly concerned are those whose distillation range extends from an initial temperature between 160.degree. C. and 190.degree. C. to a final temperature between 350.degree. C. and 390.degree. C. these limits being in no way imperative.
A large number of products are marketed as improvers of the limit filtrability temperature and the pour point of oil cuts of high paraffin content, these products being, for example:
polymers containing long chain olefins PA1 co-polymers containing alpha-olefins PA1 ethylene-vinyl acetate copolymers PA1 N-acyl aminoethylesters of acid-containing polymers, or PA1 halocarbon compounds PA1 (A) recurrent units from at least one linear .alpha.-olefin; PA1 (B) recurrent units derived from at least one .alpha.,.beta.-unsaturated dicarboxylic compound, in the form of a diacid, a lower alkyl diester or an anhydride; PA1 (C) recurrent units from at least one alkyl ester of an unsaturated monocarboxylic acid; and PA1 (D) recurrent units from styrene and/or at least one of its alkylated, halogenated or methoxylated derivatives. PA1 dodecylamine, tetradecylamine, hexadecylamine, octadecylamine, eicosylamine and docosylamine. PA1 monoethanolamine, 1-amino3-propanol, 1-amino4-butanol, 1-amino5-pentanol, 1-amino6-hexanol, 1-amino7-heptanol, 1-amino8 octanol, 1-amino10-decanol, 1-amino11-undecanol, 1-amino13-tridecanol, 1-amino14-tetradecanol, 1-amino16-hexadecanol, 2-amino2-methyl1-propanol, 2-amino1-butanol and 2-amino1-pentanol.
These products operate on the crystallization kinetics and modify the crystal size, thereby enabling the use of the suspension at a lower temperature without plugging of the pipes and the filters. The above-mentioned products do not change the temperature at which the first paraffin crystals appear. As a matter of fact it has been considered, up to now, that this temperature depended on the molecular weight and the composition of the paraffins and on the nature of the solvent.
Decreasing the cloud point of middle distillates (particularly gas oils) by means of an additive, would be of particular concern to the refiners since it would enable without modifying the distillation diagram, to meet the specifications, which tend now to become more severe.
It has now been discovered that certain chemical compounds, as hereafter defined, have the property, when added to middle distillation, to decrease the temperature at which the first paraffin crystals appear, as compared to the temperature at which these crystals appear in the absence of these additives. This property is the more unexpected as it is retained after several heating and cooling cycles and its mechanism has not yet been elucidated.
This class of chemical compounds also operates on other properties of middle distillates (particularly gas oils) by modifying the behavior of the medium containing the settled paraffins.
Thus the compounds proposed according to the invention have a substantial effect on the limit filtrability temperature and the pour point.
When paraffin crystals, whose formation results from cooling, have appeared, they normally tend to gather by gravity in the bottom portion of the container. This phenomenon, generally called sedimentation, results in the plugging of pipes and filters and is detrimental to the use of middle distillates and particularly of gas oils. The chemical compounds proposed in the invention are able to substantially decrease the sedimentation rate of the paraffins formed by cooling gas oils and other middle distillates.
Finally, the products proposed for their above-mentioned properties further impart to gas oils and middle distillates to which they are added, anticorrosion properties as concerns metal surfaces.